Resonant directional couplers



p 1961 P. G. MARIE 2,999,988

RESONANT DIRECTIONAL COUPLERS Filed March 17, 1954 4 Sheets-Sheet 1 12(2') 1256 730(1) Li'cfl)17 125/ 0) 4 6 6 t 6 6 I75 la 12-5) P) 10 1.1712/24) 7517/0) INVENTOR. Pierre G. Marie PM, W W 011mm 1717M ATTORNEY-SSept. 12, 1961 P. G. MARIE 2,999,988

RESONANT DIRECTIONAL COUPLERS Filed March 17, 1954 4 Sheets-Sheet 2 I413 20 t0 t1 1 L 20 i 22 Ta r0 r4 2,2 27 j 23 Fly. 3 F194 Fl 6 Fl 7 Hg. 8

INVENTOR.

Pierre 6. Marie BY VW' W ATTORNEYS Sept. 12, 1961 P. G. MARIE 2,999,988

RESONANT DIRECTIONAL COUPLERS Filed March 17, 1954 4 Sheets$heet 3 FIG.l5

INVENTOR. Pierre G. Marie I M, M, wmom f T /4 ATTORNEYS Sept. 12, 1961P. G. MARiE 2,999,988

RESONANT DIRECTIONAL COUPLERS Filed March 17, 1954 4 Sheets-Sheet 4INVENTOR.

Pierre 6. Marie PW, ,M,

Baum -4- Tow,

ATTORNEYS United States Patent 2,999,988 RESONANT DIRECTIONAL COUPLERSPierre G. Mari, 16 Rue de Varize, Paris, France Filed Mar. 17, 1954,Ser. No. 416,869 Claims priority, application France Mar. 23, 1953 16Claims. (Cl. 333-10) This invention relates to resonant directional waveguide couplers and more particularly to couplers which, from an inputguide carrying a totality of electromagnetic energy spread over a wideband of frequencies, sort into each of a plurality of output guides theincoming energy lying within a distinct band of frequencies or channellying within such wide band.

It is an object of the invention to provide a coupler of this type whichwill, given a totality of electromagnetic energy distributed throughouta wide band of frequencies and appearing as a progressive wavepropagated down a principal guide, extract from this totality thefraction pertaining to a specified channel and pass it into one of theoutput guides without disturbing in the principal guide the flow ofenergy proper to the other channels.

A further object of the invention is to provide a coupler of the typementioned comprising a single cavity resonator between the principalguide and each of the output guides.

A resonant directional coupler according to the invention includes acylindrical resonator coupled between tworectangular guides. In such acoupler the energy entering as a TE wave through one end of a first oneof the rectangular guides passes through the cylindrical resonator as acircularly polarized wave formed of two TE waves in quadraturerelationship and emerges as a TE wave through one end of the secondrectangular guide, if the frequency of the wave is close to the resonantfrequency of the resonator.

A number of cylindrical resonators may be coupled at one end to theinput rectangular guide and at their other ends to individual outputrectangular guides receiving the energies of the separate channels. Thecouplers are directional in the sense that they are traversed byelectromagnetic energy, when of the frequency appropriate thereto, alonga path extending from a given end of the input rectangular guide to aspecified end of the second rectangular guide. On the other hand thecouplers are two-way devices in the sense that energy of suchappropriate frequencies can pass through them in the opposite directionas well.

When for example the coupling system serves to mix in the principalguide, assumed to be coupled to a transmitting antenna, and which thenconstitutes the output guide, energies of particular Wave length rangesdeveloped by oscillators coupled to the individual guides above referredto as output guides but which on the present assumption then constitutethe input guides, it may be necessary to provide for unidirectionalenergy transmission only in order to prevent reflected waves frompassing through the separate couplers with consequent modification oftheir associated oscillator frequencies, in the event of imperfectcoupling of the antenna to the principal guide.

It is another object of the invention to provide such couplers withunidirectional properties, i.e. couplers such that they transmit energypassing from one end of the input rectangular guide in a selecteddirection to one end of the second or output rectangular guide, whereasthey do not transmit energy of the same frequency in the oppositedirection.

A further object of the invention is to provide such ice to a pluralityof energies conveyed by rectangular channel guides having an optionaldirection with respect to the main guide, i.e., the direction of channelguides and main guide being not necessarily at right angles to oneanother.

Resonant directional couplers have already been proposed in which theinput and output wave guides are coupled together by cavities of squarecross section. Such cavities may support two independent modes ofoscillation at right angles. By means of an appropriate coupling devicethese two modes may be caused to exist in phase quadrature. When sophased the combination of the two modes constitutes a Wave whichresembles a wave of circular polarization. In the central region of thecavity the wave field pattern rotates Without deformation. This ishowever no longer true in the regions of the cavity outside the centerthereof and it is not at all true in the corners thereof.

This explains why in the prior art couplers constructed according tothis principle, it is necessary separately to match each of the twowaves by means of an appropriate matching device such as an obstacle.The combination of the two matching devices however is adequate only tomatch one end of the cavity, either that connected to the input guide orthat connected to the output guide. Consequently at least two cavitiesin series must be provided between the two guides.

A further object of the invention is the provision of a directionalcoupler in which each coupling element between the input and outputguides comprises only a single cavity, which cavity requires no matchingdevice within it.

couplers adapted to couple a wide frequency band of electromagneticenergy conveyed in a main rectangular guide According to the feature ofthe invention described in the fifth preceding paragraph there isintroduced into the cylindrical resonator a body of a suitable ferrite,and there is produced within the resonator a permanent magnetic fielddirected along the axis of the ferrite body. Under these conditions thetransmission through the resonator will no longer be bi-directional, andit is even possible by suitable adjustment of the field simultaneouslyto interrupt transmission in both directions.

The invention will now be further described with reference to theaccompanying drawings in which:

FIG. 1 is a perspective view of a directional coupler according to theinvention.

FIGS. 2a-2d are vector diagrams illustrating the possible modes ofpropagation in the coupler of FIG. 1.

FIGS. 3 and 4 are diagrams, useful in explaining the operation of thecouplers of FIGS. 1 and 5, illustrating the transmission and reflectionof plane Waves at semitransparent boundaries.

FIG. 5 is a perspective view of a coupler according to the inventionincluding a single resonant cavity.

FIGS. 6-8 are plan views of irises which may be inserted into thecircular wave guide portions of the couplers of the invention.

FIG. 9 is a perspective view of a coupler according to the inventionincluding a plurality of resonant cavities.

FIG. 10 is a section taken on the line 1010 of FIG. 9.

FIG. 11 is a perspective view of a plurality of couplers according tothe invention combined into a complete channel-selecting deviceaccording to the invention.

FIG. 12 is a perspective view partly broken away of a resonantunidirectional coupler according to the invention, together with adiagrammatic showing of certain associated circuit elements.

FIGS. 13a-13c are diagrammatic representations of the exchange of energybetween the various ends of the guides making up the coupler of FIG. 12.

FIG. 14 is a diagrammatic illustration of the coupler of FIG. 12 shownconnected between a transmitter, an antenna, and a high frequency radioreceiver, and

FIG. 15 is a diagramamtic representation of a conventional lumped-elemencircuit equivalent to the directional coupler of FIG. 5.

Referring to FIG. 1, the input rectangular guide 1 is coupled to acircular guide 2 by means of a coupling aperture 3 formed in the broadside or width of the guide 1. All of the input energy is taken to bepropagated down the guide 1 in the form of a progressive TE wave.

The aperture 3 is so located in theguide, that in the absence ofcoupling the progressive TE wave existing in the guide 1 will exhibit atthat location a magnetic field which may be represented by a rotatingvector of constant modulus and lying in the plane of the guide wall, thevector rotating about the center of the aperture. The equations of themagnetic field in the guide 1 are of the well known form:

H,=H sin cos (wt-13 16) in which b represents the base of therectangular guide, H represents the magnetic field applied at theentrance of the guide parallel to the coordinate axis OZ, 0:, theangular frequency of a particular wave among the totality of energiesbeing propagated, and the phase constant in the guide. fi is thus thequotient of 211- divided by the length of the wave in the guide. H and Hare dephased by 90 with respect to each other, and their respectiveamplitudes represent the Cartesian coordinates of a vector rotating withangular velocity to and having a constant modulus under the condition:

This equation defines a quantity z which represents the distance betweenthe edge of guide 1 and the center of the aperture 3 for a wave of givenfrequency. v

The sense of rotation of the magnetic field at the location of theaperture 3 is determined by the direction of propagation of the wavedown the guide 1.

The guide 2 is positioned with its axis on the axis 4 of the aperture 3,and its diameter is such that the waves may exist therein only in the TEmode. The guide 2 is open at its lower end and may for example besoldered to the guide 1 except as to the portion 5 which extends beyondthe edge of the guide 1 and which is closed by an appropriate metallicwall.

The currents circulating in the vicinity of the coupling aperture 3 maybe represented as a plot of current lines 52 rotating without relativechange among themselves about the common axis 4 of the aperture 3 andguide 2. The wave developed Within the circular guide 2 is consequentlycircularly polarized. The sense of rotation of the electric field ofthis wave of circular polarization is indicated by the arrow 6 anddepends upon the direc tion of propagation of the TE wave within theguide 1.

It will be assumed in the following description that regardless of thetype of guide and of wave propagation, the amplitude of a wave is equalto the square root of the power transmitted thereby. Having regardsimply to the symmetry of the coupler and the linearity of the equationsof propagation in the guides, it can be shown that if a wave of unityamplitude entering through the end 7 of the guide 1 develops a wave ofamplitude p emerging through the end 8 opposite the end 7 and acircularly polarized wave of amplitude 1- ernerging from the end 9 ofthe circular guide 2 and rotating in the direction indicated by thearrow 6, reciprocally a circularly polarized wave of unity amplitudeentering at the end 9 of the guide 2 and rotating in the sense of thearrow 6 will develop in the rectangular guide 1 a Wave of amplitude 1-moving toward the end 8 and a circularly polarized wave of amplitude protating in the sense of the arrow 6 and reflected toward the output end9 of guide 2. No energy is propagated toward the end 7. Proof of thisproperty of the structure of FIG. 1 may be made in the followingfashion:

In FIG. 2a the arrow 10 represents the wave entering through the end 7,of unity amplitude, as indicated by the number 1 in parentheses in thefigure. The arrow 11 represents the Wave of amplitude p emerging fromthe end 8, and the arrow 12 represents the circularly polarized wave ofamplitude 1- rotating in the sense of the arrow 6 and emerging from theend 9.

In FIG. 2b the amplitudes and waves have been multiplied by the factorConsequently the wave entering through the end 7, represented by thearrow 10 has an amplitude of The wave emerging from the end 8represented by the arrow 11 possesses an amplitude p /'r and the waveemerging throughthe end 9 represented by the arrow 12 possesses anamplitude 5p.

FIG. 20 symbolizes a state of affairs derived from that state of aifairsshown in FIG. 2a from a consideration of the field symmetry in thesymmetry plane of the coupler (the plane containing the axis 4 andperpendicular to the axis of the rectangular guide). The representationof FIG. 2c further reflects a change of sign in the time factor in theequations of propagation and a multiplication of the amplitudes by thefactor 1/1: I The eflect of the symmetry is to replace the unityamplitude wave entering through the end 7 by an output wave of amplitudep emerging through that end. Similarly the output wave emerging from theend 8 is replaced by an entering wave of unity amplitude passing throughthat end. The output wave emerging from the end 9 is unchanged. Thechange in sign for time results in replacing the wave emerging throughthe end 7 by a wave entering through that end and in replacing the waveentering through the end 8 by a wave emerging from that end and inreplacing the wave emerging from the end 9 by a wave emerging throughthat end. Lastly, upon multiplication by the factor l/r a wave ofampltiude p/ 1' represented by the arrow 10 and entering through the end7 together with a unity amplitude wave entering through the end 9 andrepresented by the arrow 13 produce a wave of amplitude 1/1- representedby the arrow 11 emerging through the end 8.

FIG. 2d represents the superposition of the two configurationsrepresented in FIGS. 2b and 20. From an examination of this figure andbearing in mind the relation that it appears that to a unity amplitudewave entering through the end 9 (arrow 13 there corresponds a wave ofamplitude 1 emerging through the end 8 (arrow 11 and a wave of amplitudep emerging through the end 9 (arrow 12 No energy emerges from the end 7(arrow 10 From the preceding proposition it follows that if into adirectional coupler such as that of FIG. 1, there is introduced throughthe end 7 of the rectangular guide 1 electromagnetic energy of TE form,the end 8 being terminated by the characteristic impedance of the guideand if there exist in the circular guide 2 both a wave excited throughthe coupling aperture 3 and directed toward the end 9 and a wave derivedfrom the reflection of this latter wave at the end 9 and directed towardthe coupling aperture 3, the two waves being propagated in oppositesenses in the guide 2 being circularly polarized and having the samesense of rotation of their electric vectors, there will exist betweenthe values t which measures the amplitude of the wave 10 enteringthrough the end 7, r which measures the amplitude of the wave 11emerging from the end 8, t; which measures the amplitude of thecircularly polarized wave 12 passing from the coupling aperture 3 to theend 9, and r which measures the amplitude of the circularly polarizedwave 13 passing from the end 9 toward the coupling aperture, the samematrix relation as that which obtains among the amplitudes of planewaves incident upon, transmitted through and reflected from a plane,semitransparent, non-absorbing surface of transmission coeflicient 1.This relation is Referring to FIG. 3, this matrix relation implies thatif 14 is a plane, semitransparent non-absorbing surface receiving a wave20 of amplitude t this incident wave will be divided into a transmittedwave 22 of amplitude t and a reflected wave 21 of amplitude r and thatreciprocally an incident wave 23 of amplitude r will be divided into atransmitted wave 21 of amplitude r and into a reflected wave 22 ofamplitude t FIG. represents the combination of two directional couplersof the type illustrated in FIG. 1. The first coupler comprises therectangular guide 1 and the circular guide 2 coupled at the couplingaperture 3. The second comprises the rectangular guide 15 and thecircular guide 2 coupled at the aperture 16. t and r representrespectively energy entering through the end 7 and emerging through theend 8 of the guide 1. t and r represent respectively energies ofcircularly polarized waves propagated in opposite directions through theguide 2. t and r represent respectively energy emerging through the end17 and entering through the end 18 of the guide .15. Under theseassumptions the distribution of energy in the combined double coupler isthe same as the energy on the opposite sides of the semitransparentsurfaces 19 and 20 of FIG. 4.

The combination of semitransparent surfaces 19 and 20 of FIG. 4constitutes an interferometer of the Perrot and Fabry type. If thesurfaces are strongly reflecting, only waves having such as wave lengththat the distance between the planes of the surfaces 19 and 20approximates an integral number of half wave lengths will betransmitted. Thus, disregarding losses The other waves not fulfillingthis condition are reflected such that 1 is very small, and r is nearlyequal to t a B y analogy, in the double coupler of FIG. 5 the waveshaving a wave length such that the height of the cylindrical guide 2approximates an integral number of half wave lengths therefor in thatguide will be transmitted with the result that:

2= o whereas the other waves not fulfilling this condition will bereflected so that r is nearly equal to t In FIG. 15, there is shown adiagrammatic representa tion of a conventional lumped-element structureequivalent to the directional coupler of FIG. 5. In FIG. 15 the resonantcircuit comprising inductance 67 and capacity 68 connected in seriesrepresents the resonator 2 of FIG. 5 for one of its two TE modes ofvibration, and the resonant circuit comprising inductance 69 andcapacity 70 connected in series represents the same resonator 2 for itssecond TE mode. The transformers 71 and 72 represent the coupling holesbetween the resonator 2 and the currents which, in the rectangularguides 1 and 15 of FIG. 5, flow in the direction of the guide axes,Similarly the transformers 7.3 and 74 represent the coupling holesbetween the resonator 2 and the currents which, in the rectangularguides 1 and 15, flow perpendicularly to the guide axes. The currents inthe resonant circuits 6768 and 69-70 are in quadrature relationship andwhether one current lags or leads the other by a phaseshift results fromthe direction of propagation in lines7-8 and 17-18. The diagram of FIG.15 is equivalent to a duplexer.

In the double coupler of FIG. 5 the value of t as a function of t and offiequency is that of a simple cavity resonator, i.e. of a resonantcircuit. A better selectivity with respect to wave length is obtained ifthere are pro vided within the circular guide 2 a plurality of cavityresonators tuned to the central frequency of the channel to be selected,these cavities being separated from each other by irises.

The form of these irises and their mutual separations may be specifiedby computations of the type used in the filtering of guided waves. Itmay however be noted that the circularly polarized waves propagated inboth directions within the interior of the circular guide 2 are waveseach made up of a pair of TE waves in quadrature and that the irisesmust be selected and positioned with due respect for the circularpolarization present. To this end it is sufii'cient for them to have arepetitive symmetry at least threefold in nature. Most convenientlyirises having a circular aperture may be employed.

FIGS. 6, 7 and 8 show other types of irises which may be employed toseparate the cavity resonators. The iris 24 is inductive, the iris 25 iscapacitive, and both possess fourfold repetitive symmetry. The iris 26is capacitive and exhibits threefold repetitive symmetry. Apertures ofthe shape of the openings in the irises 24-26 may be substituted inplace of the coupling apertures 3 and 16.

FIG. 9 represents a double directional coupler with three resonantcavities. The guide '1 in which the energy arrives from the end 7 andwhose end 8 is connected by means not shown to the characteristicimpedance of the guide, is coupled to the circular guide 2 through anaperture 27 having the shape of the opening in iris 26 of FIG. 8. Therectangular guide 15 from which the energy emerges from the end 17 andwhose end 18 is coupled to the characteristic impedance of that guide iscoupled to the circular guide 2 through an aperture 30 having likewisethe form of the opening in the iris 26. The circular guide 2 is dividedinto three resonant cavities 39, 40 and 41 by means of irises 28 and 29of the form of the iris shown in FIG. 7. Each resonant cavity may betuned by means of four plugs. In FIG. 9 there are illustrated plugs 31and 32 for cavity 39, plugs 35 and 36 for cavity 40 and plugs 37 and 38for the cavity 41. Two additional plugs per cavity may be provided indiametrically opposite positions inasmuch as it is desirable to providefour plugs for tuning of cavities in which there exists a circularlypolarized wave made up of two TE waves. Two plugs disposed each at oneend of two perpendicular diameters would theoretically suffice, but thiswould destroy the symmetry of the circularly polarized wave.

FIG. 10 illustrates the four plugs 31-34 provided for tuning of thecavity 39.

FIG. ll represents a combination of four directional couplers ofresonant cavity type according to FIG. 9. This combination is destinedto son-t out the following channels:

(I) 3,700-3,720 mc.

(II) 3,740-3,760 mc. (I11) 3,780-3,800 mc. (IV) 3,8203,840 me.

All of these channels fall within a band of frequencies which may becollected by a receiving antenna and applied to the left end of theprincipal input guide 42. To this guide there are coupled four circularguides 43, 44, 45, 46, coupled respectively to the rectangular guides "747, 48, 49, 50. Each circular guide is coupled to two rectangular guidesby apertures such as the apertures 27 and 30 of FIG. 9. Each circularguide comprises three resonant cavities each having a height equal to ahalf wave length for a TB wave the circular guide of the mid frequencyof the channel to be selected. If for example the circular guides 43-46have a diameter D=6 cm., their out ofi wave lengths for TE waves areAssuming for the rectangular guides 37-41 the same cut oil wave length,

2b=l0.26 cm.

Hence b=5.13 cm.

Consequently the wave lengths of the waves in the circular guide and inthe rectangular guides are the same. The properties of the coupler ofFIG. 11 can then be In practice one may select for z an average value of1.11 cm. and for the heights values slightly shorter than thoseindicated. Exact tuning is then obtained by means of the plugs.

The width b of the rectangular guides being fixed at a valueapproximately equal to 5.13 ms, the height a may no longer bearbitrarily chosen. For reasons of matching it is desirable to providethat:

A Z unmw 1 (2'3 b 3.76(2b) 2 Taking for A the median wave length of theentire band, i.e. 7\=8 cm. and taking for b and D respectively 5.13 and6 cm., the value of a is 0.83 cm. in view of the fact that the value ofthe radial is unity.

In 'FIG. 11 the right end of the guide 42 and the near end of the guides47-50 are provided with terminations 51 which may for example take theform of absorbing plates of carbon or similar material. The plates areprovided with an oblique edge presented to the interior of the guides,and the plane of the plates is parallel to the height or small dimensionof the guides.

The resonant cavities which make up each circular wave guide are tunedby means of plugs in order to transmit, for example to receivers whichmay becoupled to the guides 47 and 50, energies lying within thechannels I-IV set out in the table.

It may be observed that the orientation of the guides 47-50 about theaxes of their associated circular guides may be arbitrary inasmuch ascircularly polarized waves possess rotational symmetry.

FIG. 12. illustrates a unidirectional coupler according to theinvention. A plurality of unidirectional couplers of the type shown inFIG. 12 may be combined into a complete channel-selecting deviceaccording to the invention similar to that shown in FIG. 11 but havingunidirectional transmission properties. The rectangular guides 1 and 15are positioned parallel to each other in order to facilitate thefollowing explanation. It is however to be understood that theirorientation about the axis of the circular guide 2 may be arbitrarysince '8 the waves propagated within the guide 2' are circularlypolarized. The guide 2 is coupled to the guides 1 and 15 by couplingapertures 3 and 16, respectively.

A rod of ferrite 53 is positioned coaxially within the guide 2, and awinding 54- is provided outside the guide. The rod 53 is positionedwithin the guide 2 by means of insulating disks 59 and 60 of polystyrenefor example. The winding 54 is energized from a DC. source 55 controlledby a potentiometer 56. The current flowing in the winding 54 develops aunidirectional magnetic field parallel to the axis of the circularguide. 7

In the absence of this permanent magnetic field the resonant frequencyof the cylindrical resonator 2 is the same for circularly polarizedwaves regardless of the sense of rotation of the electric vectorthereof. However in the presence of the permanent axial magnetic fieldthis is no longer true, and the two resonant frequencies correspondingto the two directions of rotation of the electric field are separate.The ferrites 'str'ongly exhibit the Faraday effect. This eifect, wellknown in optics, may be described as follows:

When a plane wave circularly polarized passes through a materialsubjected to a unidirectional magnetic field directed along thedirection of propagation, the phase velocity (i.e. the optical index ofthe material) depends upon the direction of rotation of the electricvector. The difference between the index observed in the presence of thefield and the index in the absence of that field increases with theintensity of the field and varies with the frequency of the incidentwave.

The ferrites are metallic oxides of the general formula xFe O in which xrepresents a bivalent metal such as magnesium, nickel or cobalt. Theycombine the high resistivity of oxides with the ferromagnetic propertiesof iron. In view of this high resistivity relatively thick rods of thismaterial may be positioned within a cylindrical guide without producingsevere attenuation in wave propagation.

' Two T13 waves of the same amplitude in quadrature having theirelectric vectors mutually perpendicular on the axis of the guide 2together form a circularly polarized wave. To the two possibledirections of rotation of the electric filed along the axis of the guidethere correspond two different phase velocities.

For a given unidirectional field let F be the resonant frequency ofresonator 2 when the electric field rotates in the sense of the arrow57, and let F be the resonant frequency when the electric field turns inthe opposite sense indicated by the arrow 58. If the direction ofrotation indicated by the arrow 57 is that of the circularly polarizedwave developed in the resonator 2 when the energy enters through the end7 of the guide 1, it will likewise be the sense of rotation of thecircularly polarized wave when the energy enters through the end 18 ofthe guide 15. In fact, with the arrangement of FIG. 1 a symmetry of thefields with respect to the plane of symmetry perpendicular to the axisof the cylindrical guide preserves unchanged the direction of rotationof the electric field within the resonator 2.

On the other hand the sense of rotation of the circularly polarizedwaves developed when the energy enters through the end 8 of the guide 1or through the end 17 of the guide :15 is that of the arrow 58. Indeedin these two cases the fields may be dreived from the two casespreviously discussed by considerations of symmetry with respect to theplane containing the axis of the circular guide and perpendicular to thelength of the rectangular guides, and this symmetry reverses the senseof rotation of the electric field in the resonator 2.

Thus if an electromagnetic wave has a frequency F it will traverse theresonator 2 if introduced at the end 7 or 18, and it will not traverseit if introduced at the ends 8 or 17. The possible energy transmissionsbetween the ends 7, 8 and 17, 18 for the frequency F are indicated bythe arrows in FIG. 13 in which a diagonal arrow indicates passage ofenergy through the resonator 2.

Similarly a wave of frequency F passes through the resonator 2 ifintroduced at the ends 8 or 17 and does not pass through it ifintroduced at the ends 7 or 18. The possible transmission between theends 7, 8, 17 and 18 for the frequency F are indicated by the arrows inFIG. 13b.

If the frequency of the incident wave departs widely from thefrequencies F and F no energy will pass through the resonator 2. Thepossible transmissions are then indicated by the arrows of FIG. 130. Theabsence of diagonal arrows indicates that the energy can pass downeither of the guides 1 and but cannot pass from one to the other.

The properties just discussed are utilized in the device of FIG. 14 toprotect an oscillator tube 61. The oscillator develops a band offrequencies centered on the frequency F and is coupled at the end 7 of arectangular guide 1. By the mechanism of the guides 1, 15 and 2 of FIG.14 the oscillator 61 is protected against waves reflected by an antenna62 coupled to the end 17 of the guide 15. Such reflections may occur forexample when the antenna is not exactly matched in impedance to theimpedance of the guide 15 throughout the range of wave lengths developedby the oscillator. Matched terminations 63 and 64 are located at theends 8 and 18 of guides 15 and 1. The energy developed by the tube 61follows the path indicated by the arrow 65 and is radiated by theantenna 62. The energy reflected by the antenna follows the pathindicated by the arrow 66 and is absorbed in the termination 64.

The coupler of the invention may serve as a duplexer in a radarreceiver. The tube 61 of FIG. 13 then takes the form of a pulsedtransmitter, and the termination is replaced by the radar receiver.

While the invention has been described in terms of specific embodiments,it is to be understood that variations readily occurring to the manskilled in the art are possible and that these variations fall Withinthe scope ofthe invention. Thus for example the guides 4750 may beconnected to transmitters developing energy in the separate channels,and the guide 42 may then be connected to a transmitting antenna.

I claim:

1. A wave guide transmission system comprising a first rectangular waveguide adapted to support in the TE rectangular mode a plurality ofelectromagnetic waves of different frequencies lying within a frequencyband divisible into distinct frequency channels, said guide havingformed in a wide face thereof a plurality of apertures, a plurality ofcircular wave guides associable each with one of said channels, saidcircular guides being each afiixed at one end to said first guidecoaxially about one of said apertures, and a plurality of secondaryrectangular Wave guides each having an aperture formed in a wide facethereof, each of said secondary guides being aflixed to the other end ofone of said circular guides with its aperture coaxially positionedrelative to said one circular guide, said circular guides having each aheight substantially equal to half a wave length, for waves of the TEcircular mode propagated within such circular guides, corresponding tothe median frequency of the associated one of said channels.

2. A wave guide transmission system comprising a first rectangular waveguide adapted to support in the TE rectangular mode a plurality ofelectromagnetic waves of different frequencies lying within a frequencyband divisible into distinct frequency channels, said guide havingformed in a wide face thereof a plurality of apertures having anelectrical circular symmetry, a plurality of circular wave guidesassociable each with one of said channels, said circular guides beingeach afiixed at one end to said first guide coaxially about one of saidapertures, a plurality of secondary rectangular wave guides the axes ofwhich may have any direction parallel to the wide face of said firstrectangular guide, each secondary wave guide having an aperture havingan electrical circular symmetry formed in a wide face thereof, each ofsaid secondary guides being affixed to the other end of one of saidcircular guides with its aperture coaxially positioned relative to saidone circular guide, said circular guides having each a heightsubstantially equal to half a wave length, for waves of the TE circularmode propagated within such circular guides, corresponding to the medianfrequency of the associated one of said channels, and means to terminateeach of said rectangular guides at one end thereof with itscharacteristic impedance.

3. A wave guide transmission system comprising a first rectangular waveguide adapted to support in the TE rectangular mode a plurality ofelectromagnetic Waves of different frequencies lying within a frequencyband divisible into distinct frequency channels, said guide havingformed in a wide face thereof a plurality of apertures, a plurality ofcircular wave guides associable each' with one of said channels, saidcircular guides being each afiixed at one end to said first guidecoaxially about one of said apertures, a plurality of secondaryrectangular wave guides each having an aperture formed in a wide facethereof, each of said secondary guides being affixed to the other end ofone of said circular guides with its aperture coaxially positionedrelative to said one circular guide, one or more irises in each of saidcircular guides dividing the interior thereof into a plurality ofresonant cavities, the cavities in each of said circular guides having aheight substantially equal to half the guide wave length for a wave ofthe T13 circular'mode resonating within the cavities of such circularguide, said last-named Wave having the median frequency of theassociated one of said channels, and a plurality of tuning plugsdisposed in the walls of said circular guides communicating with each ofthe cavities formed by said irises.

4. A directional filtering Wave guide' coupler system comprising aprincipal rectangular guide adapted to support in the T13 rectangularmode a plurality of electromagnetic waves covering a wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in a wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for one of said channels of substantiallyequal magnitude and in phase quadrature, a plurality of cylindricalcavity resonators each arranged coaxially with one of said apertures andafixed at one end to said guide with the end adjacent said guide closedexcept at the said aperture, said cylindrical cavity resonators havingsuch diameters as to support waves within said channels respectivelyonly according to the TE circular mode and having as their resonantfrequencies substantially the median frequencies of said channelsrespectively, and a plurality of channel rectangular guides the axes ofwhich may have any direction parallel to the Wide face of said principalrectangular guide, each channel guide being adapted to support waveswithin said band in the T13 rectangular mode and having each an aperturein one of its wide walls centered about a point at which thelongitudinal and transverse current components in said Wall are for oneof said channels of substantially equal magnitude and in phasequadrature, said channel rectangular guides being aflfixed to saidcylindrical cavity resonators with their apertures coaxial with saidcylindrical cavity resonators respectively and with the ends of saidcylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, wherebya plurality of waves falling within said wide frequency band andarriving in the TE rectangular mode from a given end of the principalrectangular guide give rise in each of said cavity resonators to acircularly polarized Wave having a given direction of rotation thereinand falling within one of said channels and further give rise to a TErectangular wave in each of said channel rectangular guides, the

wavesin said channel rectangular guides being propagated only toward agiven end thereof.

5. A directional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a 'plurality of electromagnetic waves covering a wide frequencyband divisible into distinct frequency channels, said guide having aplurality of apertures in a wide wall thereof centered re spectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for one of said channels of substantiallyequal magnitude and in phase quadrature, a plurality of cylindricalcavity resonators each arranged coaxially with one of said apertures andaflixed at one end to said guide with the end adjacent said guide closedexcept at the said aperture, said cylindrical cavity resonators havingsuch diameters as to support waves within said channels respectivelyonly according to the TE circular mode and having as their resonantfrequencies substantially the median frequencies of said channelsrespectively, said resonators further having as their heights anintegral multiple of one-half the wave length corresponding to saidmedian frequencies in the TE mode, and a plurality of channelrectangular guides the axes of which may have any direction parallel tothe wide face of said principal rectangular guide, each channel guidebeing adapted to support waves within said band in the TE rectangularmode and having each an aperture in one of its wide walls centered abouta point at which the longitudinal and transverse current components insaid wall are for one of said channels of substantially equal magnitudeand in phase quadrature, said channel rectangular guides being aflixedto said cylindrical cavity resonators with their apertures coaxial withsaid cylindrical cavity resonators respectively and with the ends ofsaid cylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, wherebya plurality of waves falling within said wide frequency band andarriving in the TE rectangular mode from a given end of the principalrectangular guide give rise in each of said cavity resonators to acircularly polarized wave having a given direction of rotation thereinand falling within one of said channels and further give rise to a TErectangular wave in each of said channel rectangular guides, the wavesin said channel rectangular guides being propagated only toward a givenend thereof.

6. A directional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of electromagnetic waves covering a wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in a wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for one of said channels of substantiallyequal magnitude and in phase quadrature, a plurality of cylindricalcavity resonators each arranged coaxially with one of said apertures andaffixed at one end to said guide with the end adjacent said guide closedexcept at the said aperture, said cylindrical cavity resonators havingsuch diameters as to support waves within said channels respectivelyonly according to the TE circular mode and having as their resonantfrequencies substantially the median frequencies of said channelsrespectively, said resonators further having as their heights anintegral multiple of one-half the wave length corresponding to saidmedian frequencies in the TE mode, at least two tuning stubs located inperpendicular radial planes in each of said cylindrical cavityresonators, and a plurality of channel rectangular guides the axes ofwhich may have any direction parallel to the wide face of said principalrectangular guide, each channel guide being adapted to support waveswithin said band in'the TE rectangular mode and having each an aperturein one of its wide walls centered about a point at which thelongitudinal and transverse current com ponents in said wall are for oneof said channels'of sub stantially equal magnitude and in phasequadrature, said channel rectangular guides being affixed to saidcylindrical cavity resonators with their apertures coaxial with saidcylindrical cavity resonators respectively and with the ends of saidcylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, wherebya plurality of waves falling within said wide frequency band andarriving in the TE rectangular mode from a given end of the principalrectangular guide give rise in each of said cavity resonators to acircularly polarized wave having a given direction of rotation thereinand falling within one of said channels and further give rise to a TErectangular wave in each of said channel rectangular guides, the wavesin said channel rectangular guides being propagated only toward a givenend thereof.

7. A directional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of electromagnetic waves covering a Wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in a wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for one of said channels of substantiallyequal magnitude and in phase quadrature, a plurality of cylindricalcavity resonators each arranged coaxially with one of said apertures andaflixed at one end to said guide with the end adjacent said guide closedexcept at the said aperture, said cylindrical cavity resonators havingsuch diameters as to support waves within said channels respectivelyonly according to the TE circular mode and having as their resonantfrequencies substantially the median frequencies of said channelsrespectively, said resonators further having as their heights anintegral multiple of one-half the wave length corresponding to saidmedian frequencies in the TE mode, at least one iris in each of saidresonators dividing the interior thereof into a plurality of partialcylindrical cavity resonators, at least two tuning stubs in each of saidpartial cylindrical cavity resonators located in perpendicular radialplanes of said resonators, and a plurality of channel rectangular guidesadapted to support waves within said band in the TE rectangular mode andhaving each an aperture in one of its wide walls centered about a pointat which the longitudinal and transverse current components in said wallare for one of said channels of substantially equal magnitude and inphase quadrature, said channel rectangular guides being aflixed to saidcylindrical cavity resonators with their apertures coaxial with saidcylindrical cavity resonators respectively and with the ends of saidcylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, wherebya plurality of waves falling within said wide frequency band andarriving in the TE rectangular mode from a given end of the principalrectangular guide give rise in each of said cavity resonators to acircularly polarized wave having a given direction of rotation thereinand falling within one of said channels and further give rise to a TErectangular wave in each of said channel rectangular guides, the wave ofsaid channel rectangular guides being propagated only toward a given endthereof.

8. A directional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of electromagnetic waves covering a wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in a wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for one of said channels of substantiallyequal magnitude and in phase quadrature, a plurality of cylindricalcavity resonators each arranged coaxially with one of said apertures andafiixed at one end to said guide with the end adjacent said guide closedexcept at the said aperture, said cylindrical cavity resonators havingsuch diameters as to support waves within said channels respectivelyonly according to the TE circular mode and having as their resonantfrequencies substantially the median frequencies of said channelsrespectively, a plurality of channel rectangular guides the axes ofwhich may have any direction parallel to the wide face of said principalrectangular guide, each channel guide being adapted to support waveswithin said band in the TE rectangular mode and having each an aperturein one of its wide walls centered about a point at which thelongitudinal and transverse current components in said wall are for oneof said channels of substantially equal magnitude and in phasequadrature, said channel rectangular guides being affixed to saidcylindrical cavity resonators with their apertures coaxial with saidcylindrical cavity resonators respectively and with the ends of saidcylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, andmeans to terminate each of said principal and channel rectangular guidesat one end thereof with its characteristic impedance.

9. A unidirectional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of electromagnetic waves covering a wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in the wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, aplurality of cylindrical cavity resonators each arranged coaxially withone of said apertures and aflixed at one end to said principalrectangular guide with the end adjacent said principal rectangular guideclosed except at said aperture, said cylindrical cavity resonatorshaving such diameters as to support waves within said channelsrespectively only according to the TE circular mode and having as theirresonant frequencies the median fre quencies of said channels, a body offerrite material supported coaxially within each of said cylindricalcavity resonators, means to generate in each of said ferrite bodies amagnetic field directed coaxially of said resonaators, and a pluralityof channel rectangular guides adapted to support waves within said bandin the TE rectangular mode and having each an aperture in one of itswide walls centered about a point at which the longitudinal andtransverse current components in said wall are for the median frequencyof one of said channels of substantially equal magnitude and in phasequadrature, said channel rectangular guides being affixed to saidcylindrical cavity resonators with their apertures coaxial with saidcylindrical cavity resonators respectively and with the ends of saidcylindrical cavity resonators opposite said principal guide closedexcept across the apertures in said channel rectangular guides, wherebya plurality of waves falling within said wide frequency-band andarriving in the TE rectangular mode from a given end of the principalrectangular guide give rise in each of said cavity resonators to acircularly polarized wave having a given direction of rotation thereinand falling within one of said channels and further give rise to a TErectan gular wave in each of said channel rectangular guides, the wavesin said channel rectangular guides being propagated only toward a givenend thereof, whereas waves coming from said given ends of said channelrectangular guidesdo not enter said cavity resonators.

10. A unidirectional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of electromagnetic waves covering a wide frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in the wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, aplurality of cylindrical cavity resonators each arranged coaxially withone of said apertures and affixed at one end to said principalrectangular guide with the end adjacent said principal rectangular guideclosed except at said aperture, said cylindrical cavity resonatorshaving such diameters as to support waves within said channelsrespectively only according to the TE circular mode and having as theirresonant frequencies the median frequencies of said channels, saidresonators further having as their heights and integral multiple ofone-half the wave length corresponding to said median frequencies in theTE mode, a body of ferrite material supported coaxially within each ofsaid cylindrical cavity resonators, means to generate in each of saidferrite bodies a magnetic field directed coaxially of said resonators,and a plurality of channel rectangular guides adapted to support waveswithin said band in the TE rectangular mode and having each an aperturein one of its wide walls centered about a point at which thelongitudinal and transverse current components in said wall are for themedian frequency of one of said channels of substantially equalmagnitude and in phase quadrature, said channel rectangular guides beingalfixed to said cylindrical cavity resonators with their aperturescoaxial with said cylindrical cavity resonators respectively and withthe ends of said cylindrical cavity resonators opposite said principalguide closed except across the apertures in said channel rectangularguides, whereby a plurality of waves falling within said wide frequencyband and arriving in the TE rectangular mode from a given end of theprincipal rectangular guide give rise in each of said cavity resonatorsto a circularly polarized wave having a given direction of rotationtherein and falling within one of said channels and further give rise toa TE rectangular wave in each of said channel rectangular guides, thewaves in said channel rectangular guides being propagated only toward agiven end thereof, Whereas waves coming from said given ends of saidchannel rectangular guides do not enter said cavity resonators.

11. A unidirectional filtering wave guide coupler system comprising aprincipal rectangular guide adapted to support in the T E rectangularmode a plurality of electromagnetic waves covering a wire frequency banddivisible into distinct frequency channels, said guide having aplurality of apertures in the wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, aplurality of cylindrical cavity resonators each arranged coaxially withone of said apertures and afiixed at one end to said principalrectangular guide with the end adjacent, said principal rectangularguide closed except' at said aperture, said cylindrical cavityresonators having such diameters as to support waves within saidchannels respectively only according to the TE circular mode and havingas their resonant frequencies the median frequencies of said channels,said resonators further having as their heights an integral multiple ofone-half the wave length corresponding to said median frequencies in theTE mode, at least two tuning stubs located in perpendicular radialplanes in each of said cylindrical cavity resonators, a body of ferritematerial supported coaxially within each of said cylindrical cavityresonators, means to generate in each of said ferrite bodies a magneticfield directed coaxially of said resonators, and a plurality of channelrectangular guides adapted to support waves within said band in the TErectangular mode and having each an aperture in one of its side wallscentered about a point at which the longitudinal and transverse currentcomponents in said wall are for the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, saidchannel rectangular guides being afiixed to said cylindrical cavityresonators with their apertures coaxial with said cylindrical cavityresonators respectively and with the ends of said cylindrical cavityresonators opposite said principal guide closed except across theapertures in said channel rectangular guides, whereby a plurality ofwaves falling within said wide frequency band and arriving in the TErectangular mode from a given end of the principal rectangular guidegive rise in each of said cavity resonators to a circularly polarizedwave having a given direct-ion of rotation therein and falling withinone of said channels and further give rise to a TE rectangular wave ineach of said channel rectangular guides, the waves in said channelrectangular guides being propagated only toward a given end thereof,whereas waves coming from said given ends of said channel rectangularguides do not enter said cavity resonators.

12. A unidirectional filtering wave guide coupler systern comprising aprincipal rectangular guide adapted to support in the T13 rectangularmode a plurality of electromagnetic waves covering a wide frequency band7divisible into distinct frequency channels, said guide having aplurality of apertures in the wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are of the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, aplurality of cylindrical cavity resonators each arranged coaxially withone of said apertures and aihxed at one end to said principalrectangular guide with the end adjacent said principal rectangular guideclosed except at said aperture, said cylindrical cavity resonatorshaving such diameters as to support waves within said channelsrespectively only according to the T13 circular mode and having as theirresonant frequencies the median frequencies of said channels, saidresonators further having as their heights an integral multiple ofone-half the Wave length corresponding to said median frequencies in theTE mode, at least one iris in each of said resonators dividing theinterior thereof into a plurality of partial cylindrical cavityresonators, at least two tuning stubs in each of said partialcylindrical cavity resonators located in perpendicular radial planes ofsaid resonators, a body of ferrite material supported coaxially withineach of said cylindrical cavity resonators, means to generate in each ofsaid ferrite bodies a magnetic field directed coaxially of saidresonators, and a plurality of channel rectangular guides adapted tosupport waves within said band in the TE rectangular mode and havingeach an aperture in one of its wide walls centered about a point atwhich the longitudinal and transverse current components in said wallare for the median frequency of one of said channels of substantiallyequal magnitude and in phase quadrature, said channel rectangular guidesbeing affixed to said cylindrical cavity resonators with their aperturescoaxial with said cylindrical cavity resonators respectively and withthe ends of said cylindrical cavity resonators opposite said principalguide closed except across the apertures in said channel rectangularguides, whereby a plurality of waves falling Within said wide frequencyband and arriving in the TE rectangular mode from a given end of theprincipal rectangular guide give rise in each of said cavity resonatorsto a circularly polarized wave having a given direction of rotationtherein and falling within one of said channels and further give rise toa TE rectangular wave in each of said channel rectangular guides, theWaves in said channel rectangular guides being propagated only toward agiven end thereof, whereas waves coming from said given ends of saidchannel rectangular guides do not enter said cavity resonators.

13. A unidirectional filtering wave guide coupler systern comprising aprincipal rectangular guide adapted to support in the TE rectangularmode a plurality of el'ec troma-gnetic waves covering a wide frequencyband divisible into distinct frequency channels, said guide having aplurality of apertures in the wide wall thereof centered respectivelyabout points at each of which the longitudinal and transverse currentcomponents in said wall are for the median frequency of one of saidchannels of substantially equal magnitude and in phase quadrature, aplurality of cylindrical cavity resonators each arranged coaxially withone of said apertures and aflixed at one end to said principalrectangular guide with the end adjacent said principal rectangular guideclosed except at said aperture, said cylindrical cavity resonatorshaving such diameters as to support waves within said channelsrespectively only according to the TE circular mode and having as theirresonant frequencies the median frequencies of said channels, a body offerrite material supported coaxially within each of said cylindricalcavity resonators, means to generate in each of said ferrite bodies amagnetic field directed coaxially of said resonators, a plurality ofchannel rectangular guides adapted to support Waves within said band inthe TE rectangular mode and having each an aperture in one of its widewalls centered about a point at which the longitudinal and transversecurrent components in said wall are for the median frequency of one ofsaid channels of substantially equal magnitude and in phase quadrature,said channel rectangular guides being afhxed to said cylindrical cavityresonators with their apertures coaxial with said cylindrical cavityresonators respectively and with the ends of said cylindrical cavityresonators opposite said principal guide closed except across theapertures in said channel rectangular guides, whereby a plurality ofwaves falling within said wide frequency band and arriving in the T13rectangular mode from a given end of the principal rectangular guidegive rise in each of said cavity resonators to a circularly polarizedwave having a given direction of rotation therein and falling within oneof said channels and further give rise to a TE' rectangular wave in eachof said channel rectangular guides, the waves in said channelrectangular guides being propagated only toward a given end thereof, andmeans to terminate each of said principal and channel rectangular guidesat one end thereof with its characteristic impedance.

'14. A directional filtering wave guide coupler system comprising aprincipal rectangular wave guide adapted to support in the TErectangular mode a plurality of electromagnetic waves covering a widefrequency band divisible into distinct frequency channels, said guidehaving a plurality of apertures in a wide wall thereof centeredrespectively about points at distances from one edge of said wide wallsubstantially equal to b i 22 1; tan )\g wherein b is the width of thesaid principal rectangular guide and R is the wave length in saidprincipal rectangular guide of the median frequencies in one of saidchannels, a plurality of cylindrical cavity resonators each arrangedcoaxially with one of said apertures and affixed at one end to saidprincipal rectangular guide with the end adjacent said principalrectangular guide closed except at said aperture, said cylindricalcavity resonators having such diameters as to support waves within saidchannels respectively only according to the T E circular mode and havingas their resonant frequencies the median frequencies of said channels,and a plurality of channel rectangular guides adapted to support wavessaid band in theTE rectangular mode and having each an aperture in oneof its wide walls centered about a point at a distance from one edge ofsaid wide 17 wall of said channel rectangular guide substantiallyequalto 1 tan wherein b is the width of said channel rectangular guideand X' is the wave length in said channel rectangular guide of themedian frequency in one of said channels, said channel rectangularguides being aflixed to said cylindrical cavity resonators with theirapertures coaxial with said cylindrical cavity resonators and with theends of said cylindrical cavity resonators adjacent a channelrectangular guide closed except across the aperture in said channelrectangular guide.

15. A wave guide coupler system comprising a first rectangular waveguide adapted to support an electromagnetic wave in the T13 rectangularmode, said guide having an aperture in a wide wall thereof centeredabout a point at which the longitudinal and transverse currentcomponents of said wave in said wall are of substantially equalmagnitude and in phase quadrature, a cylindrical cavity resonatoraflixed at one end to said principal rectangular guide coaxially withsaid aperture with the end of said cavity resonator adjacent said guideclosed except at said aperture, said cavity resonator having such adiameter as to support said wave only according to the TE circular mode,a body of ferrite material supported coaxially within said cavityresonator, a magnetic field winding disposed coaxially about said cavityresonator to apply a magnetic field to said ferrite body, and a secondrectangular wave guide adapted to support said wave in the TErectangular mode and having an aperture in one of its wide Wallscentered about a point at which the longitudinal and transverse currentcomponents of said wave in said wall are of substantially equalmagnitude and in phase quadrature, said second rectangular guide beingafiixed to said cavity resonator with its aperture coaxial with saidcavity resonators and with the end of said cavity resonator adjacentsaid second rectangular guide closed except across the aperture in saidsecond rectangular guide.

16. A wave guide coupler system comprising a first 18 I rectangular waveguide adapted to support an electromagnetic wave in the TE rectangularmode, said guide having an aperture in the wide wall thereof centeredabout a point at which the longitudinal and transverse currentcomponents of said wave in said wall are of substantially equalmagnitude and in phase quadrature, a cylindrical cavity resonatoraflixed at one end to said principal rectangular guide coaxially withsaid aperture with the end of said cavity resonator adjacent said guideclosed except at said aperture, said cavity resonator having such adiameter as to support said wave only according to the TE circular mode,and a second rectangular wave guide the axis of which may have anydirection parallel to the wide face of said first rectangular guide,said second rectangular guide being adapted to support said wave in theTE rectangular mode and having an aperture in one of its wide wallscentered about a point at which the longitudinal and transverse currentcomponents of said wave in said wall are of substantially equalmagnitude and in phase quadrature, said second rectangular guide beingaflixed to said cavity resonator with its aperture coaxial with saidcavity resonators and with the end of said cavity resonator adjacentsaid second rectangular guide closed except across the aperture in saidsecond rectangular guide.

References Cited in the file of this patent UNITED STATES PATENTS2,473,274 Bradley June 14, 1949 2,602,859 Moreno July 8, 1952 2,606,248Dicke Aug. 5, 1952 2,626,990 Pierce Jan. 27, 1953 2,667,620 Riblet Jan.26, 1954 2,713,151 Farr July 12, 1955 2,714,707 Zabel Aug. 2, 19552,719,274 Luhrs Sept. 27, 1955 2,723,377 Cohn Nov. 8, 1955 2,795,763Tillotson June 11, 1957 FOREIGN PATENTS 592,224 Great Britain Sept. 11,1953 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No,2 999 988 September 12,; 1961 Pierre Ga Mari It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below.

Column 7, line 4L9 for "radial" read radical column 8 line 75, for "FIGQ13"" read FIG, 13a 3 column l4 line 14L for "and" read an line 46 for"wire" read wide same column 14 line 72 for "side" read wide column l5line 27,, for "of" first, occurrence read for o Signed and sealed this3rd day of April 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

